Lymphocyte‐mediated cytotoxicity against tumor cells. II. Characteristics and tissue distribution of concanavalin A‐ activated cytotoxic effector cells

AbstractIn vivo or in vitro activation of cytotoxic effector lymphocytes by concanavalin A (Con A) has been shown to result in a population of effector cells exhibiting a degree of immunological specificity when Con A was present during the cytotoxic assay (Waterfield, J.D. et al., Cell. Immunol. 1975. 17: 392). In this communication we have characterized the Con A‐activated effector cell by physical criteria and tried to assign it to a given subpopulation of thymus‐derived lymphocytes. It was shown that macrophages played no role in target cell lysis in this system, nor was their presence required for Con A activation of the effector cell. The effector cell proved insensitive to anti‐Θ serum, but was classified as a T cell by the enrichment of cytotoxicity when a purified population of T cells was activated by Con A in vitro and by the failure to activate the effector cell in nude mice. Precursors of the effector cell were shown to reside primarily in the spleen, to be radioresistant up to 400 R, and to be short‐lived after adult thymectomy. Thus, the effector cell can be classified with the TI population of T cells and has similar characteristics as a cytolytically active cell described by Stobo et al. (J. Immunol. 1973. 110: 362, 652).